Optical connection device and data processing apparatus fitted with optical transmission means

ABSTRACT

An optical connection device includes at least one first rigid element fitted with an end which is preferably pointed; and at least one second element comprising a part made of elastic material such as silicon. Fasteners hold the end of the said first element against the elastic material of the said second element.

RELATED CO-PENDING APPLICATIONS

The following co-pending applications are related to the presentinvention:

U.S. Ser. No. 639,894, filed Jan. 11, 1991 - GAU 2612 358/483

U.S. Ser. No. 648,906, filed Jan. 31, 1991. - GAU 2504 250/208.1

FIELD OF THE INVENTION

The invention relates to an optical connection device for transmissionof light information; it also relates, by way of application, to a dataprocessing apparatus fitted with optical transmission means employingsuch a connection principle.

BACKGROUND OF THE INVENTION

In the data processing installations where the information is processeden masse in parallel, it is more and more necessary to have availabletransmission lines called "buses", of high performance, capable oftransmitting several Gbits/s.

Only optical technology today is capable of providing throughputsgreater than a Gbits/s, simultaneously over a large number of links,with interfaces of small dimensions and low consumption.

The European Patent Document 0 196 933 describes a system making itpossible to establish optical links between circuits of the sameapparatus. It necessitates a transparent sheet forming the rear panel ofthe housing, light sources and receivers carried by the printed circuitsand situated, preferably, in immediate proximity to the said rear panel.The diffracting optical elements and reflector elements are judiciouslyplaced on the rear panel in order to transmit the light between one ormore emitters and one or more receivers by creating multiple reflectionsin the transparent sheet. This principle implies a certain optical route"in air" outside any light guide of the fibre optic type.

Moreover, it is relatively constricting as far as the installation ofthe components on the printed circuits and the positioning of the latterare concerned.

BRIEF DESCRIPTION OF THE INVENTION

The invention envisages a different concept in which every optical routeis completely defined by light guides, with high-performance opticalconnections between them, giving rise to a minimum loss.

One aim of the invention is to propose a novel, simple, high-performanceoptical connection device, which is economical as much from the point ofview of the installation cost as from the point of view of the runningcost.

To this end, the invention relates to an optical connection device fortransmission of light information, comprising at least one first rigidtransparent element with a pointed end, at least one second element madeat least partly of transparent elastic material, and mechanical fixingmeans for forcibly applying and holding the pointed end of the saidfirst element against the part made of transparent elastic material ofthe said second element.

All of these elements are preferably made of glass or of transparentplastic material as far as the rigid parts are concerned; the elasticmaterial mentioned above is a material adapted to the transmission ofoptical signals, based on silicon or on deformable plastic such as athermoplastic of the hot-or cold-vulcanising silicone elastomer type,used especially for contact lenses.

Another aim of the invention is to apply the connection principledefined above in the architectures of data processing apparatuses(signal, information or images) comprising optical transmission meanswith high throughputs, for example of the order of several Gbits/s.

Another aim of the invention is to provide high-performance opticallinks, possibly disconnectable, between the components of a singlecircuit and/or components of neighboring circuits.

More precisely, the invention relates to a data processing apparatuswith optical transmission means for transmission of light information,comprising at least one first light guide with a pointed end made ofrigid material, at least one second light guide fitted with at least onesegment of transparent elastic material, and mechanical fixing means forforcibly applying and holding the said end against a side of the saidsegment made of transparent elastic material.

The pointed end of the said first light guide will preferably be in theshape of a cone if the guide has a cylindrical cross-section or in theshape of a dihedron if the guide has a square or rectangularcross-section. The latter characteristic will enable the direction ofthe light route to be changed by covering one face of this dihedron witha reflecting or semi-reflecting coating.

Advantageously, the dihedron of the pointed end of the first light guidecomprises two oblique facets delimiting a laterally offset ridge, one ofthe facets coming into the extension of the first light guide and theother forming a swelling on the side of the first light guideterminating in an inclined shoulder.

The invention will be better understood and other advantages of it willappear more clearly in the light of the description which follows, givensolely by way of example and by reference to the attached drawings, inwhich:

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagrammatic view of an optical connection device inaccordance with the invention;

FIG. 2 is a digrammatic, sectional view of a part of a data processingapparatus equipped with means of transmission of light informationfitted with connections in accordance with the principle of theinvention;

FIG. 3 is a diagrammatic, perspective view of another part of such adata processing apparatus;

FIG. 4 diagrammatically illustrates, in perspective, a sub-assembly ofsuch an apparatus; and

FIG. 5 diagrammatically illustrates, in perspective, a link moduleintended to be interposed between two circuits of such an apparatus.

DETAILED DESCRIPTION OF THE INVENTION

Referring more particularly to FIG. 1, a simple optical connectiondevice 11 is represented, for transmission of light information, whichcan be incorporated into any data processing or transmission systemcomprising at least one optical transmission line with a highinformation throughput. The connection device thus permits any twounits, not represented, of such a system to be connected. Here, itcomprises a first rigid element 12, made of transparent plastic materialor of glass, of circular, square or rectangular cross-section, whosefree end 13 is pointed, for example a cone or a dihedron according tothe shape of the cross-section of the rigid element 12. The shape of thelatter, in cross-section, can be different from that of those which areindicated above.

The device further comprises a second transparent parent element 15, atleast partly elastic. More precisely, in the example represented, thesecond element 15 is composed of another rigid element 17 of the sametype as the element 12 and of a pellet 16 made of transparent elasticmaterial, situated at its connecting end. The pellet 16 is in contactwith the rigid element 17. The first rigid element is contained in anopaque sheath 19 except for its pointed end 13 which projects beyond theend of this sheath. The pellet 16 and the element 17 are housedend-to-end in an opaque sheath 20, the pellet being flush with thebottom of a shallow recess formed at the end of the sheath 20, shapedand dimensioned in order to receive the corresponding end of the sheath19. This arrangement thus ensures correct positioning of the opticaltransmission elements. The device described above is finished off bymechanical fixing means for forcibly applying and holding the end 13 ofthe first element 12 against the pellet 16 made of transparent elasticmaterial. In this example, these mechanical fixing means are embodied byflanges 19a, 20a, defined at the respective ends of the sheaths 19, 20and intended to be assembled one against the other by any suitablemeans, not represented. It emerges clearly from the drawing that, whenthe flanges are thus assembled, the pointed end 13 penetrates into thepellet 16. The refractive indices of the various materials are chosen inorder to ensure light transmission without further deviations. Thepellet 16 is made of a material based on silicon, on deformable plastic,or on any other transparent elastic material with appropriate opticalproperties. It is, for example, a thermoplastic of the hot- orcold-vulcanizing silicon elastomer type such as those used for contactlenses. The deformation by compression exerted on this pellet 16 by therigid pointed end 83 has the effect of generating a reactive forceoptimising the contact with this pointed end 13. All of these elements,once assembled, reconstitute a light guide capable of transmittinginformation at a very high throughput, of the order of several Gbits/s.

In the following examples, the connection devices are exploited in orderto implement a change of orientation in the optical route of the lightinformation. In order to do this, the rigid element has a square orrectangular cross-section and its free end is in the shape of adihedron. Moreover, at least one of the faces of this dihedron iscovered by a reflecting or semi-reflecting coating.

More precisely, with reference to FIG. 2, any part of data processingapparatus is represented, especially a first light guide 30 connected toa multi-layer printed circuit 32 which comprises, buried between thelayers, a second light guide 34. As the light guide 30 is arrangedperpendicular to the plane of the printed circuit, the two light guides30, 34 are mutually perpendicular. They have a square or rectangularcross-section. With the exception of its end portion 30a, the guide 30is mounted inside an opaque sheath 36, which is not necessary for theguide 34 which is buried in the printed circuit. The latter comprises asegment made of transparent elastic material 38 assembled with at leastone rigid segment, the mounting being carried out with slightcompression of the said segment made of transparent elastic material. Inthe example represented, the segment 38 is interposed between two rigidsegments 40, 41. The connecting faces of these segments are preferablyinclined with respect to the axis of the guide, as represented.

The first light guide 30 has a rigid pointed end 30a which penetratesinto the circuit 32 and which is forcibly applied and held in thesegment made of transparent elastic material 38 of the second lightguide 34. This rigid pointed end 30a forms a dihedron 45 with a ridgewhich is perpendicular to the second light guide 34, laterally offset inthe extension of one of the lateral walls of the first light guide 30and delimited by two oblique, symmetric facets. One of these oblique,symmetric facets comes into the alignment of the main section of thefirst light guide 30 while the other delimits a lateral swelling on theend of the first light guide 30, terminating in an inclined shoulder 44.

The inclined shoulder 44 which terminates the lateral swelling of theend 30a of the first light guide 30 comes into contact with acorresponding bearing face of the opaque sheath 36. This makes itpossible to carry through the repulsion force, exerted by thetransparent elastic material 38 on the rigid pointed end 30a, to the endof the opaque sheath which is equipped with a flange similar to theflange 19a of FIG. 1, permitting it to be fixed by screws to the printedcircuit 32.

The oblique facet which comes into the alignment of the main section ofthe first light guide 30 carries a reflecting or semi-reflecting coating46 and enables, by reflection and change of direction, the light beam tobe passed from the first light guide 30 to the second 34 or conversely,while the laterally offset oblique facet on the end of the first lightguide reduces parasitic reflections by sending them onto the edges ofthe transparent elastic material and not into its axis.

If the coating 46 is completely reflecting, virtually the whole of thelight beam passes from the guide 30 into the guide 34 or vice-versa. Ifthe coating is semi-reflecting, the beam can be "shared" among severalguides. By way of non-limiting example, FIG. 3 shows a link arrangementbetween an "emitter" guide 30a linked to a source of light informationand two "receiver" guides 30b, 30c linked to various receivers. Thesethree guides, whose ends are in rigid dihedron shapes, are connected tothe same guide 34a (for example buried in a multi-layer printedcircuit), the dihedron of each guide 30 being engaged in a segment oftransparent elastic material 38a, for example based on silicon or ondeformable plastic such as a thermoplastic of the silicon elastomer typeused especially for contact lenses. The dihedron 45a of the emitterguide 30a comprises a face having a coating 46a, here completelyreflecting, which reflects the light towards the other two dihedrons.The dihedron 45b of the receiver guide 30b, which is closest, comprisesa face having a semi-reflecting coating 46b in such a way that part ofthe light beam reaches the other dihedron 45c of the receiver guide 30c.This dihedron has, on one of its faces, a coating 46c, which can becompletely reflecting or, on the contrary, semi-reflecting if otherreceivers are coupled to the guide 34a.

FIG. 4 illustrates a hybrid sub-assembly 50 capable of constituting partof a data processing 35 apparatus in accordance with the invention. Sucha sub-assembly can group together electronic processing circuits,processors and memories, etc., accessible via rows of electricalcontacts 51. According to the invention, it also comprises first and/orsecond light guides in accordance with the description above, which arehere advantageously arranged in such a way as to form at least one rowof optical contacts 52 for linking with other sub-assemblies. In theexample represented, the sub-assembly 50 comprises two rows of opticalcontacts, these being constituted by dihedron ends, of the typedescribed above.

FIG. 5 represents another component in accordance with the principle ofthe invention. It concerns a linking module 55 intended to be mountedbetween neighboring circuits or sub-assemblies. In the example, thismodule comprises a plurality of first and/or second light guidesarranged, preferably, mutually parallel. These guides are trapped in anover-molded block with the exception of their ends 56, here in the shapeof a dihedron.

The type of optical connection, which has just been described, byreversible deformation of a transparent elastic material by means of apointed rigid optical element exhibits the advantage of beingdisconnectable and of being able to replace the pointed rigid opticalelement in order to modify, possibly, the coupling characteristicsthereof (bevelled shape or reflective index of the end) or to carry outmaintenance thereon. The recommended shape makes it possible to adaptthe coupling in an optimum manner between the two optical elements whilepreserving an effective cross-section equal to the cross-section of thebar.

We claim:
 1. Data processing apparatus having optical transmission meansfor transmission of light information, comprising at least one firstlight guide with a pointed end made of rigid material; at least onesecond light guide fitted with at least one segment of transparentelastic material; and mechanical fixing means for forcibly applying andholding the said pointed end against a side of the said segment made oftransparent elastic material.
 2. Data processing apparatus according toclaim 1, wherein at least one of the above-mentioned light guides isembedded in a structure of a multi-layer printed circuit.
 3. Dataprocessing apparatus according to claim 1 wherein the second light guidecomprises a segment made of transparent elastic material assembled withat least one rigid segment; the transparent elastic material beingcompressed by the pointed end.
 4. Data processing apparatus according toclaim 1 wherein the guides have a parallelepiped cross-section, thepointed end, made of rigid material, being in the shape of a dihedronwith at least one face covered by at least a semi-reflecting coating. 5.Data processing apparatus according to claim 4, wherein the pointedrigid end, in the shape of a dihedron, exhibits a ridge which isdelimited by two oblique facets, the ridge being offset laterally withrespect to a main axis of the first light guide, one of the facetsintersecting a surface of the first light guide, the other facetprojecting to an intermediate inclined shoulder which intersects anothersurface of the guide to form a projection.
 6. Data processing apparatusaccording to claim 5 wherein the first light guide is clad with anopaque sheath provided at its end with the said mechanical fixing means;and with a bearing surface contacting the inclined shoulder in order totransfer, via the opaque sheath and thus to the said mechanical fixingmeans, a repulsion force exerted on the pointed end of the first lightguide by the said elastic segment.
 7. Data processing apparatusaccording to one of claims 1 to 6, together with at least one hybridsub-assembly including at least the first light guide arranged in atleast one row of optical contact elements for linking with othersub-assemblies.
 8. Data processing apparatus according to one of claims1 to 6, together with at least one link module between adjacent firstlight guides arranged mutually parallel to one another.
 9. An opticalconnector for light information transmission, the connectorcomprising:at least a first light guide having a rigid transparentelement terminating in a pointed end; at least one second light guidecoupled to the first and including a member of transparent elasticmaterial; and fastening means for urging the pointed end of the firstlight guide into continuous compressive contact with the elastic memberfor ensuring an uninterrupted light path between the guides.
 10. Theconnector set forth in claim 9 wherein the transparent elastic materialis a thermoplastic of the silicon elastomer type.
 11. The connector setforth in claim 9 wherein the rigid element has a parallelogram crosssection, and the pointed end is formed as a dihedron, one surface ofwhich has a coating thereon for at least partially reflecting light. 12.The connector set forth in claim 9 wherein intersecting surfaces of thedihedron pointed end form an end ridge which is laterally offset from amain axis of the rigid element;one of the intersecting surfacesappending directly from a main portion of the rigid transparent element,another of the intersecting surfaces appending to an intermediateinclined shoulder which, in turn appends to the main portion of theelement thereby forming a side projection.
 13. The connector set forthin claim 9 wherein the rigid transparent element is embraced by anopaque sheath having a section mounting the fastening means thereto;thesheath further including a bearing surface contacting the inclinedshoulder for facilitating transfer of bias force exerted on the pointedend, by the compressed elastic material, to the fastening means.